Placenta growth factor contributes to cell apoptosis and epithelial-to-mesenchymal transition in the hyperoxia-induced acute lung injury

FAM134B deletion exacerbates apoptosis and epithelial-to-mesenchymal transition in rat lungs exposed to hyperoxia

Oxygen therapy is widely used in clinical practice; however, prolonged hyperoxia exposure may result in hyperoxic acute lung injury (HALI). In this study, we investigated the role of FAM134B in hyperoxia-induced apoptosis, cell proliferation, and epithelial-to-mesenchymal transition (EMT) using RLE-6TN cells and rat lungs. We also studied the effect of CeO2-NPs on RLE-6TN cells and lungs following hyperoxia exposure. FAM134B was inhibited in RLE-6TN cells and rat lungs following hyperoxia exposure. Overexpressing FAM134B promoted cell proliferation, and reduced EMT and apoptosis following hyperoxia exposure. FAM134B activation increased ER-phagy, decreased apoptosis, improved lung structure damage, and decreased collagen fiber deposition to limit lung injury. These effects could be reversed by PI3K/AKT pathway inhibitor LY294002. Additionally, CeO2-NPs protected RLE-6TN cells and lung damage following hyperoxia exposure by ameliorating impaired ER-phagy. Therefore, FAM134B restoration is a potential therapeutic target for the HALI. Moreover, CeO2-NPs can be used for the treatment of HALI.

Molecular mechanisms underlying hyperoxia-induced lung fibrosis

Supplemental oxygen is often used to treat newborns with respiratory disorders. Exposure to high concentration of oxygen and long-term oxygen causes inflammation and acute lung injury. The acute inflammatory phase is followed by a fibroproliferative repair phase, leading to lung fibrosis. Many infants with lung fibrosis develop significant respiratory morbidities including reactive airways dysfunction and obstructive lung disease during childhood. Despite the absence of effective treatments and the incomplete understanding regarding mechanisms underlying fibrosis, extensive literature regarding lung fibrosis from in vitro and in vivo hyperoxia-exposed models is available. In this review, we discuss molecular mediators and signaling pathways responsible for increased fibroblast proliferation and collagen production, excessive extracellular matrix accumulation, and eventually, lung fibrosis. We discuss each of these mediators separately to facilitate clear understanding as well as significant interactions occurring among these molecular mediators and signaling pathways.

Bone marrow mesenchymal stem cell-derived exosomes alleviate hyperoxia-induced lung injury via the manipulation of microRNA-425

BACKGROUND

Hyperoxia-induced lung injury (HILI) is an acute lung injury (LI) induced by extended periods of exposure to hyperoxia. Alleviating LI by bone marrow mesenchymal stem cell-derived exosomes (BMSCs-Exos) and microRNAs (miRs) has been previously reported. This study is devised to probe the interaction between BMSCs-Exos and miR-425 in HILI.

METHODS

Firstly, BMSCs-Exos were isolated and identified. Then, HILI rat models and RLE-6TN cell models were successfully established and treated by BMSCs-Exos. Afterwards, functional assays were conducted to explore cell biological behaviors in models, with miR-425 expression detected. Then, the target relation between miR-425 and PTEN was clarified by luciferase reporter assay. Eventually, expression of PTEN and the PI3K/Akt axis was assessed by Western blotting and qRT-PCR.

RESULTS

BMSCs-Exos promoted miR-425 expression and attenuated HILI and H₂O₂ induced RLE-6TN cell injury as evidence by alleviated lung cell injury, decreased TUNEL-positive cells, induced cell viability and declined apoptosis (all p < 0.05). Besides, when miR-425 was knocked-down, the protective role of BMSCs-Exos in HILI was also reduced (all p < 0.05). miR-425 targeted PTEN mRNA, whose upregulation reversed the protective role of BMSCs-Exos in HILI (all p < 0.05). BMSCs-Exos improved the quenched levels of the PI3K/AKT axis in HILI (all p < 0.05).

CONCLUSION

Our data supported that miR-425 in BMSCs-Exos inhibits HILI by targeting PTEN and upregulating the PI3K/AKT axis. This study may provide personalized interventions for HILI remedy.

Placental growth factor gene silencing mitigates the epithelial‑to‑mesenchymal transition via the p38 MAPK pathway in rats with hyperoxia‑induced lung injury

Hyperoxia may cause pulmonary fibrosis in neonates and is characterized by the epithelial-to-mesenchymal transition (EMT) of alveolar epithelial cells. The placental growth factor (PLGF) gene is a member of the vascular endothelial growth factor family and is highly expressed in lung tissues that have been exposed to hyperoxia. The aim of the present study was to assess the role of PLGF in the EMT of lung tissue. Lung tissue exhibiting low PLGF expression was obtained by injecting rats exposed to hyperoxia with a PLGF-silencing lentiviral plasmid. Western blot analysis and immunohistochemistry revealed that expression levels of the EMT-related protein epithelial-cadherin were increased, whereas its inhibitor protein zinc-finger E-box binding homeobox 2 was decreased in these rats. These data demonstrated that PLGF silencing may significantly mitigate hyperoxia-induced EMT in rat lung tissue. Additionally, an increase in phosphorylated-p38 MAPK protein expression indicated that PLGF may be able to regulate hyperoxia-induced lung injury in rats via the p38 MAPK pathway.

Microarray analysis reveals the changes of circular RNA expression and molecular mechanism in acute lung injury mouse model

Acute lung injury (ALI) is a severe disease with sudden onset, rapid progression, poor treatment response, and high mortality. An increasing number of studies had found that circular RNAs (circRNAs) has significant functions in various diseases, while the role of circRNAs in ALI is not yet clear. The purpose of this study was to find circRNAs related to ALI and their mechanism of action. Expression profiles of lung circRNAs and messenger RNAs (mRNAs) were analyzed by microarray in the ALI mice models and healthy controlled mice. Differentially expressed RNAs were identified, function and pathways were analyzed by bioinformatics analysis. Moreover, the results of the microarray were verified by real-time PCR. We identified 2262 differentially expressed mRNAs and 581 circRNAs between ALI mice and control. Validation of candidate circRNAs by real-time PCR indicates that the majority of circRNAs identified by microarray are reliable and worthy of further study. ALI induced circRNAs primarily function in the metabolic regulatory process. Moreover, differentially expressed circRNAs were mainly involved in signaling pathways of mitogen-activated protein kinases, focal adhesion, FoxO, neurotrophin, and Wnt. In addition, a competitive endogenous RNA network was constructed to further interpret the molecular mechanism of ALI. This study observed significantly changed circRNAs profiles in LPS-induced mouse model and revealed a potential role of circRNAs in ALI.

Pathogenic CD8+ T Cells Cause Increased Levels of VEGF-A in Experimental Malaria-Associated Acute Respiratory Distress Syndrome, but Therapeutic VEGFR Inhibition Is Not Effective

Malaria is a severe disease and kills over 400,000 people each year. Malarial complications are the main cause of death and include cerebral malaria and malaria-associated acute respiratory distress syndrome (MA-ARDS). Despite antimalarial treatment, lethality rates of MA-ARDS are still between 20 and 80%. Patients develop pulmonary edema with hemorrhages and leukocyte extravasation in the lungs. The vascular endothelial growth factor-A (VEGF-A) and the placental growth factor (PlGF) are vascular permeability factors and may be involved in the disruption of the alveolar-capillary membrane, leading to alveolar edema. We demonstrated increased pulmonary VEGF-A and PlGF levels in lungs of mice with experimental MA-ARDS. Depletion of pathogenic CD8⁺ T cells blocked pulmonary edema and abolished the increase of VEGF-A and PlGF. However, neutralization of VEGF receptor-2 (VEGFR-2) with the monoclonal antibody clone DC101 did not decrease pulmonary pathology. The broader spectrum receptor tyrosine kinase inhibitor sunitinib even increased lung pathology. These data suggest that the increase in alveolar VEGF-A and PlGF is not a cause but rather a consequence of the pulmonary pathology in experimental MA-ARDS and that therapeutic inhibition of VEGF receptors is not effective and even contra-indicated.